Everyone realize that these masks with exhaust valves are unacceptable for Covid-19 or any other infectious disease? They would only be good for woodworking or something that you want to protect yourself against some irritant. There is a reason you rarely see masks with exhaust valves in the public much: only an idiot or somebody who doesn’t care about others would wear a mask where they would be breathing out unfiltered air through the valve.
I agree with the previous comment. You are not supposed to wear masks with ventilators.
I bought these but asked to return them because they didn’t fit right and the material was not very good quality. A mesh type of nylon. they have a velcro strap around the back and only I think three paper filters to replace the one that was in there. then the mask is useless unless you can find the right kind of filter. I do not recommend them. My request was granted to return them.